ASTM D1404 Test Method Estimation of Deleterious Particles in Lubricating Grease
8. Procedure
8.1 Use a fine, smoothing file to break sharp edges of one face of each test plate. (A sharp edge could scratch the face of the opposite plate.) Remove plastic filings and dust. Do not remove protective paper at this time.
8.2 Completely remove the tension from the spring and disassemble the apparatus from the top, Fig. 1b. Snap a test plate into each of the square recesses of holders 2 and 7 (Fig. 2); locate the plates such that the surfaces with the filed edges are opposite each other.
NOTE 5 - The square recesses should be clean, that is, free of solid material, to preclude uneven loading of the plastic plates.
8.3 Remove the protective paper from the test plates. The exposed polished surfaces must be free of scratches and dust. Remove any incidental dust with a soft brush (beware of static charges attracting more dust), damp chamois skin, or compressed-gas (ionizing-type recommended) dust remover.
8.4 Place a pea-sized (about 0.25 g), representative sample of the test grease on the face of the lower test plate. Bolt on the cap assembly, making sure the threaded pin, 9, is against one stop. Use the locking wing nut, 14, to retain this position. Turn the loading screw to apply a pressure of 200 psi [1.38 MPa] as indicated by the pointer and scale and the apparatus maker's spring calibration.
NOTE 6 - The scale indicates linear displacement and does not directly indicate pressure. The apparatus should be supplied with a calibration to convert the scale reading to pressure. (Consult the manufacturer if this calibration information is missing.) One equipment maker reported the following calibration:
Scale reading of 29 = 200 psi [1.38 mPA], more or less 5 %.
Equipment made at other times or by other manufacturers can vary and can have different calibrations.
NOTE 7 - The pressure applied to the plates determines the thickness of the grease layer between them. A pressure of 200 psi [1.38 MPa] gave a thinner layer than 100 psi [0.69 MPa], but increasing the pressure from 200 to 500 psi [1.38 to 3.45 MPa] caused very little change.
8.5 With this pressure applied, loosen the locking wing nut, 14, on the cap assembly and turn handle, 11, once as far as it will go (about 30°).
8.6 Release the spring pressure and disassemble the apparatus. Carefully remove the plastic plates from their holders.
8.7 Mark the plates for identification and remove the protective paper from the back faces. Wash the test grease from the plates with filtered Stoddard solvent (Warning: Flammable. Vapor harmful.) and blow dry with filtered air. Handle the test plates very carefully to avoid accidental scratches.
8.8 Count and record the total number of arc-shaped scratches on the two plastic test plates. See Fig. 3 for examples of different degrees of scratching.
